# Capacitor with 105 degree celsius ?

Discussion in 'Electronic Basics' started by mowhoong, Apr 8, 2005.

1. ### mowhoongGuest

Capacitor with a range of 105 Celsius & life 8000 hours? I am curious to know
who will design a circuit put under such high temp. & only last for eight thousend
hours, other component like plastic will also deform due to high temp.Do you think
it make sense ? Can any person know the reason. Thanks.

2. ### PeteSGuest

I assume you are wondering why someone might specify such a part ( T >=
105C, MTBF 8000 hrs)

There are many places we routinely put electronic equipment where the
ambient temperature can reach those levels (although we prefer them not
to).

One example is in aircraft - if there's circuitry near the leading wing
edges of a modern jet aircraft, the temperature might easily attain
100C (friction between the external air and the wing cause the heating)
and we do have circuitry there - slat sensors for example. There are
few circuits that don't require a capacitor (for bypassing / filtering)
somewhere. You have obviously found one that is going into a harsh
environment.

On another note, the temperature within a box stuffed with electronic
equipment is going to rise above external ambient - the only question
is how much.

The spec limit for most military parts is usually -55C to +125C,
incidentally.

Cheers

PeteS

3. ### tlbsGuest

Another application for high(er) temperature components is the
automotive industry. Inside of an automobile computer module, on a hot
day, under the hood (bonnet) the ambient temperature can reach 65C.
Then, if the automobile is started, some of the semiconductor junctions
can quickly reach 85C or higher with the surrounding components heating
up almost as high.

A properly designed system would rarely use components that were only
rated for the maximum stressors (temperature, voltage, etc.).
Components are generally de-rated, so that 105C capacitor might be used
in such an automotive application.

BTW, I design space and military systems and we have to use components
rated for -55C to +125C almost exclusively. Some of the semiconductors
are rated for even higher temperatures.

5. ### Lord GarthGuest

Besides the heat of drilling, what is the temperature at say 4000 feet?

6. ### mowhoongGuest

Thanks for your reply, I remenber i dementle one of the branded hair dryer,
i found a simple circuit with a E.capacitor hide inside the heater coil.
The reason that the capacitor would not burn out due to a motor fan turn
on when ever you switch on the hair dryer.How ever i will not design such
like this with high risk if the motor fan slower than before due to some
problum like the grease dry out in the motor bearing, a agree with me ?

8. ### mowhoongGuest

Hi John.
What kind of Downhole equipment is? you will expect the solder tin melt when it
reach 187 C. do you mean the electronic circuit board in the downhole ?

10. ### Lord GarthGuest

The temperature below the sea bed is way cold!!! I expected it to start
getting
hot but then the first site wasn't drilling too deep ... < 600 meters below
the
sea bed.